Numerical modelling of large landslides stability and runout

International audienceModelling of flow-like landslides is one of the possible approaches that can be used to simulate landslide instability and flow development. Models based on continuum mechanics and associated with a versatile rheological model are usually preferred to predict landslide runout and relevant parameters. A different approach has been used in this research. We have developed a 2-D/3-D finite element code to analyse slope stability and to model runout of mass movements characterised by very large displacements. The idea was to be able to use different material laws already known, tested and verified for granular materials. The implemented materials laws include classical elasto-plasticity, with a linear elastic part and different applicable yield surfaces with associated and non-associated flow rules. The application of Finite Element methods to model landslide run-out, contrasts previous research where typically depth-averaged equivalent-fluid approaches were adopted. The code has been applied to the simulation of large rock avalanches and rapid dry flows in different materials and under different geological and geomorphological conditions

Experimental analysis and theoretical interpretation of triaxial loadcontrolled loose sand specimen collapses

A series of triaxial load-controlled tests is performed. Finite load increments are imposed. The single load-steps are followed by a time period during which the axial load is kept constant. At low stress levels the mechanical response is stable and characterized by a continuous decrease in strain rate with time. At higher stress levels, the mechanical response changes and, subsequently, the collapse takes place. The collapse is unexpected and occurs at a stress level less than that associated with the steady state, experimentally observed by performing strain triaxial controlled tests. In order to interpret such a behaviour, a theoretical discussion is introduced. This is based on a dynamical reinterpretation of the micromechanical fabric rearrangement of granular assembly. In particular, the role played by the kinetic energy of the system, as well as that played by the anisotropy of the microstructure, have been analysed